Conventionally, a method is proposed, wherein in case of a synthetic resin bottle which is hard to form integrally with a handle, due to a resin property thereof as in polyethylene terephthalate, a synthetic resin parison and a handle body are separately formed, the handle body is inserted into a forming mold by a handle holder, the synthetic resin parison is transferred to the forming mold, the forming mold is closed, and the blow-molding is performed (Japanese Unexamined Patent Publication No. 99350/1983).